In the H.264/AVC video coding standard dated March 2005, each access unit (p. 4, section 3.1, definition of “access unit”) comprises a coded primary picture for providing the required information for representation of a coded moving picture. An access unit may further contain one or more redundant coded pictures, which “have no normative effect on the decoding process.” Section 7.4.3 (“Slice header semantics: redundant_pic_cnt”) of these standards states: “There is no required decoding process for a coded slice or coded slice data partition of a redundant coded picture. When the redundant_pic_cnt in the slice header of a coded slice is greater than 0, the decoder may discard the coded slice. NOTE 6—When some of the samples in the decoded primary picture cannot be correctly decoded due to errors or losses in transmission of the sequence and a coded redundant slice can be correctly decoded, the decoder should replace the samples of the decoded primary picture with the corresponding samples of the decoded redundant slice. When more than one redundant slice covers the relevant region of the primary picture, the redundant slice having the lowest value of redundant_pic_cnt should be used.” Thus, the presence of one or more redundant coded pictures in the encoded bitstream is optional and the intended use (but not a required use) of a redundant coded picture is the correction of transmission errors in the primary coded picture. The redundant coded picture feature of H.264 has been presented as follows; “Redundant slices (RS), an error/loss robustness feature allowing an encoder to send an extra representation of a picture region (typically at lower fidelity) that can be used if the primary representation is corrupted or lost.”
The pre-published new version of MPEG-4 AVC/H.264 standard further provides scalable video coding tools and allows a decoder to recover either the primary coded picture or a higher resolution form of the primary coded picture. However, these new standard coding tools involving increased implementation complexity have not been quickly adopted by industry.
Skilled artisans will appreciate that elements in the FIGS. are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the FIGS. may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.